Revealing mistake: In the shot where the Rohan refugees are heading into Helm's Deep, the scale of the shot is wrong. On the right side of the screen, the refugees walk up the ramp into the gatehouse and on the left side of the screen, the Deeping Wall extends, with figures moving along the wall. The Deeping wall should be about even with ramp up to the Keep, if not a little bit forward, which means the figures along the wall should be at least the same size as the figures walking up the ramp. However, the figures along the wall, are much smaller, as if the Deeping Wall was pushed back further than the ramp. The right side shot was filmed as live action and the left side shot was filmed using the miniature of Helm's Deep and then the shots were merged together. (00:11:25)
Continuity mistake: During the Warg attack, as the first Warg falls on top of Gimli, in the wide shot we see the area they fall, past the Warg. Later, when the second Warg climbs on top of the corpses and Gimli, in the wide shot, as Aragorn throws the spear we see the area past the second Warg again. The landscape, including patches of grass and rocks, is different in the two shots. This has nothing to do with the angle of the shots. (00:11:30)
Revealing mistake: During the Warg battle, as Aragorn slices off the head of a Warg rider, in the background on the hill there are two Rohan riders on horseback, one on a brown horse, one on a white horse, riding down the hill chasing after Orcs on foot. There are many shots after, including Aragorn throwing the spear into the Warg saving Gimli, and Theoden stabbing the Warg in his mouth. The next shots of Aragorn are when he stabs a Warg rider. The background plate is the same hill and the same two Rohan riders on horseback are still riding down the hill chasing after the Orcs on foot. Obviously these two pieces of footage were shot consecutively and were cut and separated, and other various shots were inserted in between them. (00:11:35 - 00:12:20)
Revealing mistake: When Aragorn saves Gimli from the warg, the spear he throws is CG. He barely tosses the thing with little more thrust than his forearm can allow, and it pierces straight through the warg's tough hide. (00:12:10)
Deliberate mistake: During the Warg attack, Aragorn jumps onto a moving Warg and in a close-up, he headbutts the Orc rider. In the next shot, as they're riding, they pass a Rohan rider on a white horse. In the background there are dead bodies strewn on the hill to their right, as they're approaching a huge bush also to their right. As they continue moving, there are multiple shots, including Aragorn falling and stabbing the Orc. In the shot just after the Orc rips off the Evenstar, the Orc falls off the Warg and it is the very same background plate as before, as they pass that huge bush to their right. These two pieces of footage were obviously one sequence that was split and other shots were inserted in between them. (00:12:30)
Continuity mistake: When Aragorn fights with the Orc riding the Warg, Aragorn knocks the Orc off and he falls to the ground. Then the Warg tumbles off the cliff with Aragorn. If you notice, the Orc falls a fair distance from the cliff, but when Legolas and Gimli ask him what happened, he is much closer to the cliff edge. (00:12:45 - 00:13:40)
Deliberate mistake: During the Warg attack, Aragorn is being dragged by the Warg and is heading for the cliff. In the very last wide shot of Aragorn, from behind his head, we see the hillside and riders behind the Warg, where they just came from. Next, we see a couple of shots of Gimli finishing off a Warg. In the next wide shot, the hillside including riders and bodies is the same one as earlier, only it's been flipped. (00:12:50)
Revealing mistake: In Emyn Muil, just after Frodo says, You will lead us to the Black Gate," Sam and Frodo are following after Gollum. You see Frodo, with Sam trailing, come around a large rock formation from the left of the screen, then Frodo passes a large round boulder on his right and starts to run down a slope towards the camera. As Sam passes the same large boulder on his right, you can see it shake from him brushing against it. (00:13:40)
Continuity mistake: When the Uruk-hai run through the rock canyon carrying Merry and Pippin, it's obviously the same rock canyon that Aragorn, Legolas and Gimli run through when Aragorn says, "Not idly do the leaves of Lorien fall." However, when the Uruks run through it, many false rock formations and extra running footage were added which not only changes the appearance of part of the canyon between the two shots, but also makes it seem like a longer distance through the same canyon. (00:14:40 - 00:18:00)
Revealing mistake: The very first shot of the Uruk-hai running through the rock canyon is the exact same shot that is shown in the last shot of this scene, just after Pippin bites the Lorien brooch off his cloak. Even though in between those two shots, all the Uruk-hai have been running until they meet up with the Orcs. In between those two shots, the rock formation shown behind the Uruk who lifts his fist up is also quite different in the next successive shot, when the Orcs approach the Uruks. (00:14:40 - 00:16:50)
Revealing mistake: When the Uruk-hai are running through the rock canyon while carrying the Hobbits, the Uruk with the painted white hand on his face holds up his right fist. In the theatrical release and regular DVD, a second Uruk then asks of the painted one, "What is it, what do you smell?" and he answers, "Manflesh." The very next shot is of Pippin saying, "Aragorn," followed immediately by the second Uruk saying, "They've picked up our trail." The Uruk who should have the painted hand on his face no longer does. He gives a low growl, then all the Uruk-hai run again. However, in the extended DVD, same scene, when the painted Uruk holds his fist up, it cuts to the Orcs hiding behind the rock, and the very next shot is of those two Uruks, and just like in the regular DVD, the Uruk who is supposed to have the painted hand on his face, does not. It is that Uruk who later in the scene says, "Manflesh," and unlike the regular DVD, without the painted hand on his face. Side note: It may be a different Uruk standing next to the 'second Uruk', in the questionable shots and that's why he doesn't have a painted face, but either way, it's still a mistake between shots. (00:14:50)
Continuity mistake: Éowyn and many of the refugees are shown as they see Helm's Deep in the distance. In the first wide shot, Éothain and Freda are riding on the horse and a particular rock formation is seen way in the distance. They keep riding towards Helm's Deep, which we see in the next shot. In the children's next close-up, they are now right in front of that rock formation that was shown in the earlier shot. This is not due to zooming. The two pieces of footage were switched, so as to have their close-up seen last. (00:14:55)
Continuity mistake: When Gimli is about to tell Eowyn that Aragorn fell, Gimli's axe has Orc blood on it, in the next shot there is no blood. There's not enough time for him to have cleaned his axe. (00:16:40)
Audio problem: On the Deeping Wall, Theoden says, "Draw all our forces behind the wall..." but Theoden's lips are moving before we hear him say those words. (00:17:10)
Continuity mistake: When Saruman and Wormtongue look down from Orthanc at the Uruk-hai army, it is spread out across the plain in front of the tower. What happened to the vast caverns which had been dug into the ground? Some are shown off to the left of shot, but the landscape had earlier been shown as much more pitted in other scenes. (00:17:30)
Deliberate mistake: In one of the first shots of Aragorn, Legolas and Gimli, we see them running on top of a hill, with the camera sweeping over them. In that scene, Legolas' quiver is leaning on his left side and Aragorn's sword is on the wrong side. This shot is flipped. (00:17:35)
Other mistake: In this scene, Legolas says, "The Uruks turn Northeast. They're taking the Hobbits to Isengard." This is a mistake because Aragorn, Gimli, and Legolas are chasing the Uruks on a westerly course towards Isengard. If the Uruks had turned Northeast, they would have almost doubled back on the trio. (This is in the "Special Extended Edition" DVD.) The Uruks were taking the closest way to Isengard, across terrain, not traveling by common roads. In the book they traveled without rest. There's no reason to believe they would have diverted from their Western course to Northeast temporarily, that would have slowed them down. (00:19:00)
Deliberate mistake: First there's a shot of Saruman as he communicates with Sauron using the palantir, then a shot of Barad-dur. Next we see the Orcs at Orthanc pulling down trees and a shot of a tree falling into the cavern below. In FotR, just after Gandalf catches the moth atop Orthanc, we see a shot of a tree falling into the cavern down below. These are the exact same shot, only it's been flipped in this movie. (00:20:00)
Continuity mistake: Just before Brego comes up to an unconscious Aragorn, his sword is lying on his left side, perpendicular to his body, with the blade facing towards his back and the hilt facing his front. In the next shot, before Aragorn even rolls over onto his back, the blade is now pointing up his back and the hilt is at his thigh. Also once again, the tear in the coat and shirt at Aragorn's left shoulder is very different in both shots, as it is in many of the following shots too. (00:20:55)
Continuity mistake: When Brego finds Aragorn at the riverbank, he puts his head to him and the horse is only wearing a halter, with no bit in his mouth and a rope hanging from the halter. In the close up shots that follow, in particular when Aragorn views Helm's Deep, obviously the rope is being used as a rein, but we can clearly see that the horse now has a bit in his mouth, where there was none before. (00:21:15 - 00:44:50)
Answer: The movie makes it clear that Gandalf has lost some of his memory and his personality has changed. Gandalf actually did die and pass over to the "other side", as it were but was sent back to complete his task. However, he was sent back as a similar, but different entity. Gandalf the White does not have all the memories of Gandalf the Grey, at least at first. He doesn't even remember that he used to be called Gandalf the Grey until someone points this out to him. It is implied that Gandalf doesn't even remember Sam until Aragorn mentions him. Gandalf then searches his memories and remembers who Sam is and his eventual importance to Frodo's quest. When he finally remembers this, he is pleased that Sam went with Frodo, as he will play a crucial role near the end of the journey.